Alkaline-setting resin-starch reaction product and methods of preparation thereof



Patented Aug. 25, 1953 ALKALINE-SETTING RESlN-STAEOH BEAC- TION PRODUCTAND METHODS OF PREP- ARATION THEREOF Carl 0. Kesler and Erling T.Hiermstad, Cedar Rapids, Iowa, assignors to Penick & Ford, Ltd.,Incorporated, Cedar Rapids, Iowa,'a corpow tion of Delaware No Drawing.Application September 12, 1950, Serial No. 184,512

1 This invention relates to alkaline-setting resin-starch reactionproduct and methods of preparation thereof. More particularly, itpertains to the manufacture of a reaction product of undispersed starchand a resin capable of being polymerized to a water-insoluble stateunder alkaline conditions.

Reference is made to the copending application of Carl C. Kesler, SerialNo. 60,641, filed November 17, 1948, now Patent Number 2,626,934.

As set out in said above application, when starch is gelatinized in thepresence of small proportions of alkaline-setting resins, such asketone-aldehyde resins or resorcinol-aldehyde resins, and suificientalkaline materials to bring the pH of the paste somewhat higher than isnecessary to set or harden the resin alone, the resulting paste oradhesive will develop a high degree of water insolubility when dried.These alkaline-setting resins were found to be very efllcient ininsolubilizing starch films, as little as.

from 2 to 5% on the starch being effective. This seems to indicate thatsuch resins become chemically bound to the cooked or dispersed starchand when dried the starch-resin complex polymerizes to the insolublestate.

In the majority of commercial applications, starch is suspended in waterand heated until the granules are gelatinized. The gelatinization ofstarch is a complex phenomenon which is not entirely understood at thepresent time. The term gelatinization as generally used means theswelling of the starch granules in a water suspension to the point wherethe suspension becomes a more or less clear, homogeneous, and gelatinouspaste of dispersed starch granules.

It is known that starches derived from various species of plants becomeswollen when heated in water to certain specific temperature ranges. Itis also known that some types of starch swell much more readily thanothers. The rate of swelling or gelatinization of starches and the rateof disintegration or breakdown of the swollen is first obtained. As theheating is continued, a

point is reached where the viscosity begins to drop and this fall inviscosity usually continues indefinitely as long as the paste is heatedat a 16 Claims. (01. 260-9) I 2 constant temperature above thegelatinization temperature range of the starch. starches derived fromdifferent species of plants, or starches which have been chemicallymodified, show different rates of viscosity breakdown on continuousheating of their cooked pastes. The rate of viscosity breakdown willalso be proportional to the degree of mechanical agitation and shearingapplications.

forces to which the paste is subjected. Since in most commercialapplications it is necessary to maintain the viscosity of the starchpastes within specified limits, users of starch have constantly soughtstarches which have the lowest rate of viscosity breakdown under theirparticular conditions of, use. This is especially true in applicationswherein the starch paste is recirculated by pumps ior long periods oftime through various types of adhesive transferring equipment, forexample, machinery for forming corrugated board. In applications such asthis, the viscosity breakdown of starch pastes on continuousrecirculation and agitation constitutes a very real and serious problemand often results in delays in production schedules and poor quality offinished products. There has, therefore, been a need for a starch whichwill resist breakdown in viscosity after being gelatinized, especiallyunder strongly alkaline or acidic conditions. Such a starch would findconsiderable acceptance by users of starch in a variety of industrialHowever, although considerable knowledge is available concerning methodsor modifying starches to increase their rate of gelatinization andgranule dispersion, very little has been heretofore known about means ofreducing gelatinization rates and stabilizing starch pastes againstviscosity breakdown on agitation.

An object of the present invention is to prepare starches which afterbeing gelatinlzed under neutral conditions in the absence or chemicalswelling agents will retain a relatively constant paste viscosity whenagitated at a constant temperature for long periods of time. Anotherobject is the preparation of starches which when gelatinized in thepresence oi. chemical swelling agents such as alkali, will be much moreresistant to breakdown in paste viscosity on agitation than are thenatural varieties of starch and their ordinary modifications. Anotherobject is the preparation of starches which, when gelatinized and mixedwith acids or both acid-setting resins and acidic catalysts, will resistbreakdownin paste viscosity on agitation. A specific object is thepreparation of starches which, when gelatinized in the presence ofsubstantial proportions at alkali and then mixed with a large proportionof raw or unswollen unmodified starch, will retain a relatively constantviscosity on being recirculated through machinery used for theproduction of corrugated board. Other objects of the invention will beobvious as the specification proceeds.

We have-discovered in addition to the discovery outlined in saidapplication, Serial No. 60,641, regarding the insolubilization ofgelatinized starch by means of small proportions of alkaline-settingresins that alkaline-setting resins will combine with starch which iseither in the unswollen, filterable, granule state or hydrated only tothe degree that substantially no birefringent crosses can be observedunder polarized light in a microscope and substantially no dispersion orleaching of the granule constituents away from granule proper hasoccurred. We have discovered that by regulating the proportion ofalkaline-setting resin which is combined with starch granules with adegree of hydration maintained within these limits, we can preparestarches which, after being substantially gelatinized with heat orchemical swelling agents, or both, are much more resistant to breakdownin paste viscosity on agitation over long periods of time than are thestarches from which they are made. We have also discovered thatextremely small proportions of alkaline-setting resins will produce verygreat increases in paste viscosity stability provided the resins arereacted or combined with starch granules which are not hydrated beyondthe limits specified above.

The process by which these new products may be prepared consists ofadding to a mixture of undispsersed granule starch and water a smallamount of a water-soluble alkaline-setting resin, or necessarycomponents for forming such resins, sufiicient alkali to bring the pH ofthe suspension to within a range of '7 .0 to 11.0, and heating 'themixture at temperatures below the gelatinization temperature range ofthe starch. This general process may be carried out in a number ofdifferent ways. The resin may be reacted with the undispersed starchwhen it is suspended in water and the product used directly withoutfurther purification or drying, or the product may be dewatered, washed,and dried in standard starch processing equipment. In a differentprocess, the starch may first be made alkaline and dewatered in a vacuumtype rotary filter to a cake containing approximately 45% moisture and asolution of the resin sprayed on the surface and drawn into the cake bythe vacuum. In this case the reaction is completed by passing the cakethrough a dryer at normal starch drying temperatures. A third variationof our general process is to intimately mix starch containing from 3 tomoisture with solutions containing the resin and alkali, agitating themixture at temperatures below the gelatinization temperature range ofthe starch, and then evaporating out the excess water. Other variationsof the process will be obvious to those skilled in the art.

We have found that the water-soluble, alkaline-setting resins will reactwith undispersed granule starch under the conditions described to yieldproducts with increased stability of paste viscosity. The termalkaline-setting resins refers to such resins which, though still in thewater-soluble state, may befurther polymerized to a state ofwater-insolubility under alkaline conditions. Included are thewater-soluble ketone aldehyde resins, resorcinol aldehyde resins, andphenol-aldehyde resins.

The term undispersed granule starch" refers to starch granules which arehydrated only to a degree within the limits expressed as from theunswollen granule state to the point where substantially no birefringentcrosses can be observed under polarized light in a microscope andsubstantially no dispersion or leaching of the granule constituents awayfrom the granule proper has occurred. For example, when unmodified cornstarch is heated in a neutral water suspension in the absence ofchemical swelling agents of swelling inhibitors to the temperature atwhich its birefringent crosses disappear and then the addition of heatis stopped, the granules are in the undispersed state and are capable offunctioning efliciently in the above described processes.

In general, the factors of concentration, pH, type and modification ofresin, moisture present, and reaction temperature, etc. have an effecton the degree of paste-viscosity stabilization obtained by our process,and a proper balancing of conditions is necessary to achieve the mostsatisfactory result. For example, at lower reaction temperatures, thereaction mixture should be at a higher pH in order to obtainsatisfactory stabilization. Therefore, in the different variations ofour process, it'is necessary to adjust these factors in such a mannerthat the degree of viscosity stabilization desired for certain specificapplications is obtained. The degree of viscosity stabilization may bewidely varied, depending on the proportion of resin combined with thestarch granules. For some applications it is desired to have a productwhich will have increased viscosity stability after gelatinization inwater which is neither strongly acid nor strongly alkaline. We havefound that by reacting from .05 to .5% by weight of anacetone-formaldehyde resin with unswollen, unmodified corn starch, aproduct of this nature is obtained. In other applications, such asalkaline adhesives and the carrier portion of corrugating pastes, aproduct which will have increased viscosity stability when cooked instrongly alkaline conditions is desired. Since the rate of viscositybreakdown of gelatinized starch increases as the pH of the paste is mademore alkaline, we have found that somewhat higher proportions ofalkaline-setting resins must be combined with the unswollen starch inorder to secure the desired viscosity stability when the product isgelatinized in alkali. Generally, we have found that from .5 to 2.0% byweight of an acetone-formaldehyde resin reacted with unswollen,unmodified corn starch yields products which have the desired viscositystability when used in typical alkaline adhesive or corrugating pasteformulation.

The degree to which the starch granules should be hydrated, within thelimits specified above, depends on the subsequent processing ordisposition of the reaction product. If the reaction product is to bedried and stored or shipped, it is convenient to react starch which isnot hydrated beyond the filterable state. The reaction product maytherefore be readily dewatered and dried in standard starch processingequipment. If the reaction product is to be used-in its finalapplication without dewatering and drying, the starch granules may behydrated to a slightly greater degree.

The starch-alkaline setting resin reaction product is adapted for manycommercial applications. Close control of viscosity is essential duringthe application of textile warp sizes, textile stabilizing starchesagainst viscosity breakdown,

and are intended to illustrate but not limit our invention:

EXAMPLE 1 To a water suspension of unmodified corn starch containing42.5% of starch solids is added .3% of sodium hydroxide and 25% ofacetoneformaldehyde resin solids based on the starch. This resin is madeby the Bakelite Corporation and is designated as Bit-18648. Thesuspension is agitated for 2 to 4 hours at 125 F., then the starch isneutralized to pH 6.5 with hydrochloric acid, dewatered in a filter,washed free of salt, and dried. This product, when tested in 9. CornIndustries Viscometer, using 100 grams oi the product per 1000 grams ofa water suspension adjusted to pH 6.5, a propeller speed of 60 R. P. M.,and a paste temperature of 211 F., showed a viscosity of 1192gram-centimeters after 1 hour and 1152 gram-centimeters after 2 hours,or a breakdown viscosity of 40 gram-centimeters between 1 and 2 hours. Asuspension of commercial unmodified corn starch under the sameconditions showed a viscosity of 548 gram-centimeters after 1 hour and428 gram-centimeters after 2 hours, or a breakdown in viscosity of 120gram-centimeters between 1 and 2 hours. A description of the CornIndustries Viscometer and procedure for testing viscosity of starches isgiven in the Analytical Edition of the Journal of Industrial andEngineering Chemistry, volume 19, page 16, January 15, 1947.

EXAMPLE 2 To 1000 grams of commercial corn starch containing 2% sodiumhydroxide is added 5 grams of acetone-formaldehyde resin (Resin No. BR16648 made by Bakelite Corporation) diluted with 50 grams of water. Thestarch is then alternately kneaded andpassed through screens until auniform dispersion of the resin solution in the starch is obtained. Themixture is then heated in a dough mixer to 180 F., held at thistemperature for minutes, and then cooled. This product, when tested in aCorn, Industries Viscometer, using 100 grams of the product per 1000grams of a water suspension adjusted to pH 6.5, a propeller speed of 60R. P. M., and a paste temperature of 211 F., showed a viscosity of 1240gram-centimeters after 1 hour and 1200 gramcentimeters after 2 hours, ora breakdown in viscosity of 40 gram-centimeters between 1 and 2 hours inthe viscometer.

EXAMPLE 3 To 'a water suspension of unmodified corn starch containing43% of starch solids is added .3% of sodium hydroxide and 1.0% ofacetoneformaldehyde resin based on the starch. This is Resin No. BR16648, made by Bakelite Corporation). The suspension is agitated at 130F. for 2 to 4 hours, then dewatered and dried. This product when used asthe carrier portion in the following corrugating starch formula produceda corrugating adhesive 01' good viscosity stability.

6 Currier-portion 150 lbs. of resin starch 2602 lbs. water Heat starchand water to F. Add 25 lbs. caustic soda in 82 lbs. water Hold at 120F..i'or 10 minutes Add25 lbs. borax C001 to 115 F.

Uncooked Portion 825 lbs. unmodified corn starch 1216 lbs. cold waterThe carrier and uncooked portions were mixed and the resulting paste runin a Langston Corrugator using .016 joint jute liners and .009 straw asthe medium. No additional freshly-prepared paste was added during thisrun. The single face and double backer roll settings were .012 inch andthe operating speed used was 300 to 325 feet per minute. The viscosityof the paste was measured at intervals using a Penick and Fordcorrugating viscometer, an orifice type viscosimeter with a water timeor 18.5 to 19.5 seconds at 75 F. The viscosities of samples taken fromthe return line over a period 01' 2 hours were:

During corrugating runs made under the same conditions, using standardstarches in the carrier portion, viscosity breakdown of from an initialviscosity of 45 seconds to 25 to 30 seconds is ordinarily obtained.

EXAMPLE 4 This example illustrates the use or alkalinesetting resin inthe formulation of an acidic corrugating adhesive. In this formula theacetoneformaldehyde resin is reacted with ungelatinlzed starch tostabilize the carrier starch against viscosity breakdown, while theurea-formaldehyde resin is added to the carrier portion aitergelatinization for the sole purpose of imparting a degree of waterinsolubility to the corrugating paste on drying.- The corrugating pasteis made as follows:

Carrier portion Cold water, 200 lbs.

Unmodified corn starch, 200 lbs.

2 lbs. of caustic soda dissolved in 45 lbs. of water is added slowly Addacetone-formaldehyde resin-4V lbs.

(Resin No. BR 16648, made by Bakelite Corporation) Warm to F. and holdat 130 F. for 15 to 30 minutes Add water, 2215 lbs.

Heat to 190 F.

Neutralize to pH 6 (approximately) with alum (A12(SO4)3) Addurea-formaldehyde resin, 100 lbs.

(Uiormite 430, made by Rohm and Haas Company) Add alum (Ala(S04)a) to pH4.0

Hold at 190 F. for 15 to 20 minutes Cool to F.

- 7 Uncooked portion Pounds Unmodified corn starch 1250 Cold water 1400The carrier and uncooked portions are then mixed and agitated untiluniform viscosity for machine operation is obtained. This corrugatingpaste was run in a Langston Corrugator. The

EXAMPLE To a water suspension of unmodified corn starch containing 45%of starch solids is added 1.0% of resorcinol-formaldehyde resin solidsand 0.3% of formaldehyde based on the starch, and sufficient sodiumhydroxide to bring the pH of the suspension to 11.0. The resorcinolformaldehyde resin is supplied by the Bakelite Corporation and isdesignated as QC-17626. The suspension is agitated for 6 hours at 130F., neutralized to pH 6.0 with hydrochloric acid, then dewatered in a.suction filter, and the starch cake dried to approximately a moisturecontent. This product, when tested in a Corn Industries Viscometer,using 100 grams of the product per 1000 grams of a water suspensionadjusted to pH 6.5, a propeller speed of 60 R. P. M. and a pastetemperature of 211 F., showed a viscosity of 800 gram-centimeters after1 hour and 712 gramcentimeters after 2 hours, or a breakdown inviscosity of 88 gram-centimeters between 1 and 2 hours.

EXAMPLE 6 To a water suspension of unmodified corn starch containing 45%starch solids is added 1.0% of phenol-formaldehyde resin solids and 3%formaldehyde based on the starch, and sufficient sodium hydroxide tobring the pH of the suspension to 8.5. The phenol-formaldehyde resin issupplied by Reichold Chemical Company and is designated as Plyophen6000. The suspension is agitated for 16 hours at 80 F., then dewateredin a suction filter, the starch cake dried to approximately a 10%moisture content, and heated for four hours at a temperature of 150 F.This product, when tested in a Corn Industries Viscometer, using 100grams of the product per 1000 grams of a water suspension adjusted to pH6.5, a propeller speed of 60 R. P. M., and a paste temperature of 211F., showed a viscosity of 660 gram-centimeters after 1 hour in theviscometer and 580 gram-centimeters after 2 hours, or a breakdown inviscosity of 80 gram-centimeters between 1 and 2 hours.

While, in the foregoing specification, we have set out certain examplesin considerable detail for the purpose of illustrating embodiments ofthe invention, it will be understood that such details may be variedwidely by those skilled in the art without departing from our invention.

We claim:

1. In a process for preparing from alkaline setting resins and granulestarch a reaction product characterized by being susceptible togelatinization to form pastes having stabilized viscos ties, the step ofreacting granule starch in a ater medium at a pH fro'm"7.0 to 11.0 withfrom .05to 2.0% on a starch basis of awatersoluble alkaline settingresin selected from the group consisting of ketone-aldehyde resins.resorcinol-aldehyde resins, and phenol-aldehyde resins, by heating saidreactants, at temperatures below the normalgelatinization temperaturerange of the starch, said starch granules being at no time hydrated tothe degree that substantial leaching out of the granule constituentsinto the water occurs.

2. Theprocess of claim I in which the alkalinesetting resin is aketone-aldehyde resin.

3. The process of claim 1 in which the alkalinesetting resin is aresorcinol-aldehyde resin.

4. The process of claim 1 in which the alkalinesetting resin is aphenol-aldehyde resin.

5. The process of claim 1 in which the alkalinesetting resin isacetone-formaldehyde resin.

6. In a process of preparing from granule starch and alkaline-settingresins a reaction product characterized by being susceptible togelatinization to form pastes having stabilized viscosities, the stepsof intimately mixing substantially dry granule starch containing solublealkali and from 3% to 10% moisture with .05% to 2.0% of a water solublealkaline-setting resin based on the starch, said resin being selectedfrom the group consisting of ketone-aldehyde resins, resorcinol-aldehyderesins, and phenolaldehyde resins, and heating said mixture undernon-gelatinizing conditions without any substantial leaching out of theconstituents of the starch granules.

7. In a process of preparing from granule starch and alkaline-settingresins a reaction. product characterized by being susceptible togelatinization to form pastes having stabilized viscosity, the steps ofintimately mixing substantially dry, undispersed, granule starchcontaining soluble alkali and from 3% to 10% of moisture with a watersolution of a water soluble alkaline-setting resin containing from .05%to 2.0% resin solids based on the starch, said resin being selected fromthe group consisting of ketone-aldehyde resins, resorcinol-aldehyderesins, and phenol-aldehyde resins, and drying the mixture with heat atnon-gelatinizing temperatures below the temperature at which substantialleaching out of the granule constituents into the water occurs.

8. In a process of preparing from granule starch and alkaline settingresins a reaction product characterized by being susceptible togelatinization to form pastes having stabilized viscosities, the stepsof intimately mixing undispersed, granule starch with water, from .05 to2.0% of a water-soluble alkaline-setting resin based on the starch, andsufllcient alkali to produce a pH of from 7.0 to 11.0 in the mixture,and drying the mixture with heat at nongelatinizing temperatures belowthe temperature at which substantial leaching out of thegranuleconstituents into the water occurs said resin being selected from thegroup consisting of ketone-aldehyde resins, resorcinol-aldehyde resins,and phenol-aldehyde resins.

9. The reaction product of undispersed, granule starch and .05 to 2.0%of a water-soluble alkaline-setting resin prepared by the process ofclaim 1.

10. The reaction product of undispersed, granule starch and .05 to 2.0%of a water-soluble 9 ketone-aldehyde resin prepared by the process ofclaim 2. Y

11. The reaction product of undispersed, granule starch and .05 to 2.0%of a water-soluble resorcinol-aldehyde resin prepared by the process oi.claim 3.

12. The reaction product of undispersed, granule starch and .05 to 2.0%or a water-soluble phenol-aldehyde resin prepared by the process ofclaim 4.

13. The reaction product of undispersed, granule starch and .05 to 2.0%of a water-soluble acetone-formaldehyde resin prepared by the process orclaim 5.

14. In a process for preparing from granule starch and alkaline-settingresins a reaction product characterized by being susceptible toelatinization to form pastes having stabilized viscosities, the steps ofpreparing a mixture of starch in the granule form in a water medium at apH of 7.0 to 11.0 with from .05% to 2.0% on a starch basis or awater-soluble alkalinesetting resin selected from a group consisting ofketone-aldehyde resins, resoricinol-aldehyde resins, and phenol-aldehyderesins, and heating said mixture at non-gelatinizing temperatures belowthe temperature at which substantial leaching out or the granuleconstituents into the water occurs.

15. In a process for preparing from granule starch and alkaline-settingresins a reaction product characterized by being susceptible togelatinization to form pastes having stabilized viscosities, the stepsor intimately mixing granule starch with water, from .05% to 2.0% on astarch basis of a water-soluble resin selected from a group consistingof ketone-aldehyde, resorcinolaldehyde, and phenol-aldehyde resins, andsumcie'nt' alkali to produce a pH of 7.0 to 11.0 in the mixture, anddrying the mixture with heat at non-gelatinizing temperatures below thetemperature at which substantial leaching out of the ranule constituentsinto the water occurs.

16. In a process for preparing from alkaline setting resins and granulestarch a reaction being at no time hydrated to the degree that leachingout of the granule constituents away from the granule proper occurs sothat said starch granules remain in filterable: condition uponcompletion of said reaction.

CARL C. KESLER.

ERLING T. HJERMSTAD.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,053,850 Sturken Sept. 8, 1936 2,318,560 Ripper May 4, 19432,362,086 Myers et a1. Nov. 7, 1944 2,407,071 Gill et a1. Sept. 3, 19462,489,170 Wooster et a1. Nov. 22, 1949 2,529,851 Scnutchfleld Nov. 14,1950 2,626,934 Kesler Jan. 27, 1953

16. IN A PROCESS FOR PREPARING FROM ALKALINE SETTING RESINS AND GRANULESTARCH A REACTION PRODUCT CHARACTERIZED BY BEING SUSCEPTIBLE TOGELATINIZATION TO FORM PASTES HAVING STABILIZED VISCOSITIES, THE STEP OFREACTING FILTERABLE, GRANULE STARCH IN A WATER MEDIUM AT A PH FROM 7.0TO 11.0 WITH FROM .05 TO 2.0% ON A STARCH BASIS OF A WATER-SOLUBLEALKALINE SETTING RESIN SELECTED FROM THE GROUP CONSISTING OFKETONE-ALDEHYDE RESINS, RESOCINOL-ALDEHYDE RESINS AND PHENOLALDEHYDERESINS BY HEATING SAID REACTANTS UNDER NON-GELATINIZING CONDITIONS, SAIDSTARCH GRANULES BEING AT NOT TIME HYDRATED TO THE DEGREE THAT LEACHINGOUT OF THE GRANULE CONSTITUENTS AWAY FROM THE GRANULE PROPER OCCURS SOTHAT SAID STARCH GRANULES REMAIN IN FILTERABLE CONDITION UPON COMPLETIONOF SAID REACTION.